This is an older Paul Dupre X3 hard rubber mouthpiece for clarinet, it measures 1.00 mm.
Physically this piece is in pretty nice condition outside of the hard rubber oxidation. The outer body, beak and shank are all in nice shape and someone did recently re-cork this piece. Its facing profile of the table, tip and side rails is also in good shape showing minimal cosmetic blemishing. This piece takes the air in easy and plays with a rich response warm in color.
The tip opening on this piece measures .040” / 1.00 mm.